An Exploratory TMS Study on Prefrontal Lateralization in Valence Categorization of Facial Expressions

Area of Science:

• Neuroscience
• Cognitive Psychology

Background:

• Converging evidence suggests the dorsolateral prefrontal cortex (DLPFC) plays a role in emotional processing.
• The specific involvement of the left versus right DLPFC in recognizing different emotions remains unclear.

Purpose of the Study:

• To investigate the causal role of the left and right DLPFC in encoding the valence of emotional facial expressions.
• To determine if there is lateralization of function within the DLPFC for processing positive and negative emotions.

Main Methods:

• Transcranial magnetic stimulation (TMS) was applied over the left DLPFC, right DLPFC, and a control vertex site.
• Participants categorized facial expressions as positive or negative while receiving TMS.
• Reaction times for valence categorization were measured.

Main Results:

• Interference with both left and right DLPFC significantly delayed valence categorization compared to control stimulation.
• The delay in categorization was similar for both positive and negative emotional expressions.
• No significant valence-related lateralization was observed in the DLPFC's role in emotion recognition.

Conclusions:

• The study did not find evidence for valence-specific lateralization in the DLPFC for emotion recognition using TMS.
• Both left and right DLPFC appear to be involved in processing the valence of emotional facial expressions without clear hemispheric differentiation.
• Further research may be needed to explore potential methodological limitations and alternative explanations.